President Obama announced Friday, Feb 22 that about 100 U.S. troops have been deployed to the West African country of Niger, where defense officials said they are setting up a drone base to spy on al-Qaeda fighters in the Sahara, The Washington Post reports.

It was the latest step by the Pentagon to increase its intelligence-gathering across Africa in response to what officials see as a rising threat from militant groups.

In a letter to Congress, Obama said about 40 U.S. service members arrived in Niger on Wednesday, bringing the total number of troops based there to “approximately” 100. He said the troops, which are armed for self-protection, would support a French-led military operation in neighboring Mali, where al-Qaeda fighters and other militants have carved out a refuge in a remote territory the size of Texas.

The base in Niger marks the opening of another far-flung U.S. military front against al-Qaeda and its affiliates, adding to drone combat missions in Afghanistan, Yemen and Somalia. The CIA is also conducting drone airstrikes against al-Qaeda targets in Pakistan and Yemen.

Obama did not explicitly reveal the drone base in his letter to Congress, but he said the U.S. troops in Niger would “provide support for intelligence collection” and share the intelligence with French forces in Mali.

A U.S. defense official, speaking on the condition of anonymity to provide details about military operations, said that the 40 troops who arrived in Niger on Wednesday were almost all Air Force personnel and that their mission was to support drone flights.

The official said drone flights were “imminent” but declined to say whether unarmed, unmanned Predator aircraft had arrived in Niger or how many would be deployed there.

The drones will be based at first in the capital, Niamey. But military officials would like to eventually move them north to the city of Agadez, which is closer to parts of Mali where al-Qaeda cells have taken root.